To solve this, we need to note that book pages are usually printed on both sides of a sheet of paper. This means that if a page is torn out, both the front and back are removed (e.g., pages 7 and 8 are on the same sheet).
Pages 7 and 8 are part of the same sheet, so tearing them out means 1 sheet is removed.
Pages 100 and 101 are on the same sheet, so this is 1 more sheet.
Pages 222 and 223 are also on the same sheet, so this is 1 more sheet.
Thus, 3 sheets of paper were torn out, meaning a total of 6 pages were removed.